The invention relates to vehicle pneumatic tires and more particularly to a vehicle pneumatic tire with properties for travel in the flat state, wherein a toroidal support device is arranged on the inside of a tubeless tire mounted on a rim.
Efforts have been under way for a long time to design a vehicle pneumatic tire which is puncture-proof and self-sealing in order to obtain a run-flat tire. For this purpose, it is known to fill out the pneumatic vehicle tire following manufacture with foam material (cf. German Disclosures Nos. 19 36 526, 15 05 029, 16 05 664). Upon occurrence of a puncture, the inner area in the tread zone comes to apply against the area in proximity of the beads of the tire. Thereby occurs a substantial fulling activity and, in the case of a vehicle continuing to travel under load, a marked friction between the inner areas of the tire, which phenomena results in rapid destruction of the tire. Moreover, there exists the risk that, as a result of the fulling under load, the tire beads may detach from their fixed seat on the rim so that the tire separates from the rim. In any event, in the case of a flat tire, ability to properly steer the vehicle is lost.
Complete filling of the tire with foamed material results in a tire offering a substantially poorer travel comfort. Therefore, tires foam-filled in this manner are suitable only for vehicles intended for special applications, such as vehicles designed for emergency use in natural catastrophes, for bulletproof tires, or the like. To this factor one must add that the pressure brought about by the filling with foam material is reduced with time as a result of diffusion or other factors.
In order to prevent the separating of the beads from their fixed seat on the rim, it is furthermore known in the art to arrange a toroidal support device at the bottom of the rim which fills the remaining free space within the cross-section of the rim and the beads supported thereupon and clamps the beads rigidly or elastically against their seat areas on the rim. As a result, detachment of the beads from the rim during travel in the flat condition is prevented. Moreover, the toroidal support device whose radially external circumferential area is situated substantially at the level of the radially outer edges of the rim flanges or extends only slightly therebeyond offers an additional support area for the central zone of the tread section of the tire upon travel in the flat state (cf. German Disclosure No. 23 39 516 or U.S. Pat. No. 4,059,138).
In the case of another support device for run-flat tires, the toroidal support body projects cross-sectionally substantially beyond the maximum diameter of the rim flanges radially outwardly and far into the interior of the inflated tire. The radially internal foot section of the support body situated in the rim area has a reinforced section situated at the level of the tire beads forcing the beads against the seat areas in the rim. The section of the support body projecting therebeyond and connected therewith as a one-piece element is designed in the shape of a torus and has a substantially circular cross-section whereby, upon the use of the pneumatic tire, there remains between the inner surface of the inflated tire and the outer surface of the toroidal support body a sickle-shaped clearance which, with its cross-sectional edges, extends down into the bead area. Owing to this design, the friction between the support body and the tire is substantially reduced in normal operation. The toroidal support body consists of a rubbery material having closed and pressurized gas or air cells. On the inside of the toroidal support body there can also be provided an air chamber inflatable by means of a separate valve from the outside. In any event, the air chambers and cells of the support body are sealed with respect to the cross-sectionally annular space between the support body and the tire. As a result of the inflation pressure of the tire, the cross-section of the support body comes to be compressed whereas, upon the flattening of the tire, the support body comes to expand cross-sectionally as a result of the internal pressure in the cells or air chambers (cf. French Pat. No. 1,390,440).